[BUG] On Firefox web interface crashes upon opening details dialog for torrent with too many cached pieces #809

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1. event

   added

   bugSomething isn't workingSomething isn't working

   on Jul 25, 2026
2. event

   added a commit that references this issue on Jul 25, 2026

   limit max number of pieces shown in details dialog to 8192 YouROK#809

   6bf9415
3. tsynik commented on Jul 28, 2026

   

   tsynik

   on Jul 28, 2026

   Collaborator

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   We will not limit pieces amount as exact parts which must be shown are unknown.
4. tsynik

   closed this as not plannedon Jul 28, 2026
5. tsynik

   reopened this on Jul 28, 2026
6. nfvelten commented on Sep 1, 2026

   

   nfvelten

   on Sep 1, 2026

   Contributor

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   I tried to pin this down and ended up ruling out the obvious cause, so posting the measurements rather than a patch.

   The map's canvas is sized in TorrentCache/index.jsx:

   const piecesInOneRow = Math.floor(canvasWidth / pieceSizeWithGap)   // 14 + 3 = 17
   const height = Math.ceil(source.length / piecesInOneRow) * pieceSizeWithGap

   Measured canvas limits here (Chromium 6.1 and LibreWolf, Firefox engine): max height 65535 in both, max square side 16384 in Chromium and 23168 in Firefox.

   At a normal dialog width that is nowhere near the limit:

   pieces        320      480      640      900     1200     1600
    10000       9452     6086     4607     3281     2431     1819
    25000      23613    15181    11492     8177     6086     4522
    50000      47226    30362    22984    16354    12155     9044
   

   So 10k pieces in a 900px dialog is a 3281px canvas, which allocates fine. Rebuilding the map and redrawing costs about 83 ms per poll at 10k pieces and 161 ms at 50k, which is sluggish but not fatal. Neither explains a white screen.

   What does break is a narrow measured width, because piecesInOneRow collapses and the height explodes:

   N=10000   breaks once width <= 50px
   N=25000   breaks once width <= 118px
   N=50000   breaks once width <= 220px
   

   and those sizes genuinely fail to allocate, verified rather than assumed:

   canvas 900x3281   usable = true
   canvas 51x56117   usable = true
   canvas 221x66079  usable = false
   canvas 900x100000 usable = false
   

   There is also a latent divide-by-zero next to it. For any canvasWidth between 1 and 16, piecesInOneRow is 0, so height becomes Infinity. The if (!canvasWidth || !height) return guard does not catch it because Infinity is truthy, and every x then comes out NaN via i % 0. Chromium silently clamps that canvas to height 0, so the map just renders blank.

   That would fit "dialog opens, spinner, then white screen" if the width is measured while the dialog is still animating open, since react-measure reports the intermediate size. But I could not confirm that is what you hit, because at a steady 900px your 10k pieces should be fine.

   @event could you check, with the DETAILS dialog open on the problem torrent: the torrent's total piece count (not just cached), your window width, and devicePixelRatio? That would say whether this is the narrow-width path or something else.

   Either way both look worth guarding: floor piecesInOneRow at 1, and cap the canvas height, shrinking the drawn piece size to fit instead of growing the canvas. That keeps every piece on screen, so it does not run into the objection above about limiting the piece count. Happy to send that as a PR if you want it.
7. mikilion commented on Nov 3, 2026

   

   mikilion

   on Nov 3, 2026

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   Here are the requested diagnostic details captured from Firefox:

   • Window width (window.innerWidth): 2287
   • Device pixel ratio (window.devicePixelRatio): 0.8955223880597015
   • Total piece count (PiecesCount): 1366

   Console Error Log

   DOMException: CanvasRenderingContext2D.translate: Canvas is already in error state.
       qe index.jsx:89
       qe index.jsx:65
       Bl React
       unstable_runWithPriority scheduler.production.min.js:18
       React 4
       unstable_runWithPriority scheduler.production.min.js:18
       React 4
       unstable_runWithPriority scheduler.production.min.js:18
       React 3
       F scheduler.production.min.js:16
       onmessage scheduler.production.min.js:12
       EventHandlerNonNull* scheduler.production.min.js:12
       l (index):1
       <anonymous> index.js:4
       l (index):1
       <anonymous> React
       l (index):1
       <anonymous> React
       l (index):1
       447 main.4e5714d6.chunk.js:1
       l (index):1
       t (index):1
       r (index):1
       <anonymous> main.4e5714d6.chunk.js:1
   2.7912f39c.chunk.js:2:1017670
   Uncaught DOMException: CanvasRenderingContext2D.translate: Canvas is already in error state.
       qe index.jsx:89
       qe index.jsx:65
       Bl React
       unstable_runWithPriority scheduler.production.min.js:18
       React 4
       unstable_runWithPriority scheduler.production.min.js:18
       React 4
       unstable_runWithPriority scheduler.production.min.js:18
       React 3
       F scheduler.production.min.js:16
       onmessage scheduler.production.min.js:12
       EventHandlerNonNull* scheduler.production.min.js:12
       l (index):1
       <anonymous> index.js:4
       l (index):1
       <anonymous> React
       l (index):1
       <anonymous> React
       l (index):1
       447 main.4e5714d6.chunk.js:1
       l (index):1
       t (index):1
       r (index):1
       <anonymous> main.4e5714d6.chunk.js:1
   main.4e5714d6.chunk.js:1:311223